JP2015230179A - Board inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a board inspection device which absorbs influence of noise due to contact resistance, for example, in real time and is desirable for inspections using low-current or low-voltage electric signals.SOLUTION: The board inspection device applies an electric signal to a conductive pattern 110 of a circuit board 11 to inspect the electric characteristics of the circuit board 11. The board inspection device includes a voltage measuring terminal 156, a current supplying terminal 154, and a voltage corrector 3. The voltage measuring terminal 156 and the current supplying terminal 154 are in contact with the conductive pattern 110. The voltage corrector 3 has an instrumentation amplifier 30 capable of removing noise in the circuit formed of the voltage measuring terminal 156, the current supplying terminal 154, and the conductive pattern 110. The voltage corrector 3 corrects the potential difference between the voltage measuring terminal 156 and the current supplying terminal 154 through a control loop formed of the instrumentation amplifier 30.

Description

  The present invention relates to a board inspection apparatus suitable for inspecting a circuit board using an electric signal having a low current or a low voltage.

  2. Description of the Related Art Conventionally, there has been known a board inspection apparatus for inspecting the quality of a circuit board by applying an electric signal to a conductor pattern of a circuit board and detecting the electric signal of the conductor pattern. Patent Document 1 discloses a resistance measuring device as this type of substrate inspection device.

  The resistance measurement apparatus of Patent Document 1 includes a voltage source that can output a high voltage and a current source that can output a high current, and applies an inspection current to the object to be measured via a probe, thereby The generated voltage is measured, and the resistance value of the device under test is calculated based on the inspection current and the measured voltage.

JP 2006-30131 A

  In order to meet the increasing demand for higher performance, smaller size, and lighter weight in recent electronic products, conductor patterns on circuit boards are becoming smaller and higher density, and electronic components are being built in. Under such circumstances, for example, by applying a semiconductor manufacturing process to substrate manufacturing, a circuit board having a high-density conductor pattern (hereinafter sometimes referred to as a high-density fine conductor pattern) close to a semiconductor is realized. Is becoming more realistic.

  Here, generally, the allowable current and the withstand voltage of the conductor pattern in the circuit board are determined by the width of the conductor pattern and the interval between the conductor patterns. Specifically, the thinner the conductor pattern, the smaller the allowable current. Moreover, the withstand voltage is lower as the distance between the conductor patterns is smaller.

  Therefore, when trying to inspect a circuit board having the above-described high-density fine conductor pattern, the current and voltage of the measurement signal must be significantly lower than the current and voltage of the measurement signal applied to the conventional circuit board. it is conceivable that. However, the lower the current and voltage of the measurement signal, the greater the influence of noise from the contact resistance between the measurement terminal and the substrate.

  In this regard, the configuration of Patent Document 1 described above outputs a high current or a high voltage from the current source or the voltage source, thereby destroying impurities present at the contact portion of the probe as a measurement terminal and improving the contact state. Thus, it is assumed that the resistance value of the object to be measured can be accurately measured.

  However, since the configuration of Patent Document 1 needs to apply a high current or a high voltage to the conductor pattern of the substrate, the conductor pattern is destroyed even if an attempt is made to inspect a high-density fine conductor pattern with a small allowable current or withstand voltage. It is very likely that Therefore, the resistance measuring device of Patent Document 1 cannot cope with inspection of a circuit board in which the above-described conductor pattern is miniaturized and densified.

  The present invention has been made in view of the above circumstances, and an object thereof is to absorb the influence of noise due to contact resistance or the like in real time, and is a substrate inspection apparatus suitable for inspection using a low-current or low-voltage electric signal. Is to provide.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to the viewpoint of this invention, the board | substrate inspection apparatus of the following structures is provided. That is, this board inspection apparatus applies an electric signal to the conductor pattern of the circuit board and inspects the electric characteristics of the circuit board. The substrate inspection apparatus includes a first measurement terminal, a second measurement terminal, and a voltage correction unit. The first measurement terminal and the second measurement terminal are in contact with the conductor pattern. The voltage correction unit includes an instrumentation amplifier capable of removing noise in a circuit including the first measurement terminal, the second measurement terminal, and the conductor pattern. The voltage correction unit corrects a potential difference between the first measurement terminal and the second measurement terminal through a control loop including the instrumentation amplifier.

  That is, a potential difference occurs between two measurement terminals that should ideally have the same potential due to a voltage drop due to the contact resistance between the first measurement terminal, the second measurement terminal, and the conductor pattern. Further, by detecting the voltage drop due to the contact resistance with the first measurement terminal or the second measurement terminal, the detection voltage increases, and the inspection accuracy is lowered. In this regard, according to the above configuration, the voltage drop due to the contact resistance can be corrected, and therefore the potential difference between the first measurement terminal and the second measurement terminal can be held to be zero. Thereby, when inspecting the circuit board, the accuracy of the inspection can be further improved without being affected by the contact resistance between the two measurement terminals and the conductor pattern. In particular, by using an instrumentation amplifier having a high common-mode signal rejection ratio (CRMM), it is possible to reliably correct a voltage drop due to contact resistance between the two measurement terminals and the conductor pattern.

  In the substrate inspection apparatus, it is preferable that the instrumentation amplifier has two differential amplifier circuits that are symmetrical to each other.

  Thereby, common input signals such as noise due to contact resistance generated between the two measurement terminals and the conductor pattern can be removed, and the inspection accuracy of the circuit board can be further enhanced.

  In the substrate inspection apparatus, it is preferable that the number of amplifiers included in the control loop is one or two including the instrumentation amplifier.

  That is, in general, the shorter the control loop for correcting the voltage drop, the faster the voltage can be stabilized. In this regard, in the above configuration, the amplifier included in the control loop is only the instrumentation amplifier, or only the instrumentation amplifier and one amplifier, so the control loop can be physically shortened. It can be corrected at the moment when the voltage drop occurs. As a result, the voltage drop can be corrected at high speed and reliably in the voltage correction unit.

  In the substrate inspection apparatus, it is preferable that the amplification factor of the instrumentation amplifier is set to 1 time.

  As a result, the instrumentation amplifier can stably operate at a gain of 1 ×, so that it is possible to reliably remove the influence of contact resistance or the like generated between the two measurement terminals and the conductor pattern. .

  The substrate inspection apparatus preferably further includes an operational amplifier having an amplification factor of -1.

  As described above, by using the stable amplification state of the operational amplifier having the amplification factor of −1 without using the operational amplifier in the open state, a substrate inspection apparatus having a highly accurate voltage correction unit can be realized.

  The substrate inspection apparatus preferably has the following configuration. That is, the instrumentation amplifier includes a non-inverting input terminal, an inverting input terminal, and an output terminal. The operational amplifier includes a non-inverting input terminal, an inverting input terminal, and an output terminal. The non-inverting input terminal and the first measurement terminal are electrically connected. The inverting input terminal, the output terminal, and the second measurement terminal are electrically connected. The output terminal and the inverting input terminal are electrically connected. The non-inverting input terminal is electrically connected to the ground.

  Thereby, it is possible to correct the potential difference between the two measurement terminals to be zero with a simple configuration.

  The board inspection apparatus includes two voltage measurement terminals so as to include the first measurement terminal, and two current measurement terminals so as to include the second measurement terminal, and the two current supply terminals are interposed therebetween. Then, a current is applied to the conductor pattern, and the substrate is inspected using a four-terminal method in which the voltage of the conductor pattern is detected from the two voltage measurement terminals.

  Thereby, in the board | substrate inspection apparatus using a 4 terminal method, the voltage drop by the contact resistance of a measurement terminal and a conductor pattern can be correct | amended in real time.

1 is a schematic side view showing an overall configuration of a substrate inspection apparatus according to an embodiment of the present invention. The figure which shows the principle of the test | inspection of a board | substrate. The equivalent circuit diagram of a test | inspection of a board | substrate. The figure which shows the structure of 4 terminal methods. The figure which shows the control loop which removes the noise by a voltage correction part. The figure which shows the structure of a voltage correction part. The figure which shows the internal circuit of instrumentation amplifier. The figure which shows the operation area | region of amplifier. The figure which shows the structure of the modification of the voltage correction part of this invention.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic side view showing an overall configuration of a substrate inspection apparatus 10 according to an embodiment of the present invention. FIG. 2 is a diagram showing the principle of substrate inspection. FIG. 3 is an equivalent circuit diagram of the substrate inspection.

  As shown in FIG. 1, the substrate inspection apparatus 10 has a housing 28. In the internal space of the housing 28, a substrate mounting table 20 for mounting the circuit board 11 to be inspected, a first inspection unit 21, and a second inspection unit 22 are provided.

  The substrate mounting table 20 is configured to be capable of mounting the circuit board 11 to be inspected. The first inspection unit 21 is located above the circuit board 11 placed on the board placing table 20. The second inspection unit 22 is located below the circuit board 11 placed on the board placing table 20. Each of the inspection units 21 and 22 includes an inspection jig 23 having a large number of probes (measurement terminals) 15 and a holding body 24 that holds the inspection jig 23.

  In addition, the substrate inspection apparatus 10 includes a jig moving mechanism 25. The jig moving mechanism 25 is configured so that the first inspection unit 21 and the second inspection unit 22 can be appropriately moved in the internal space of the housing 28.

  The board inspection apparatus 10 configured as described above moves the inspection units 21 and 22 with respect to the circuit board 11 placed on the board mounting table 20, so that the circuit board 11 has a conductor pattern 110. The probe 15 can be brought into contact with the formed test point.

  As shown in FIG. 1, the upper and lower inspection units 21 and 22 each have a current supply unit 17, a current measurement unit 18, and a voltage measurement unit 19 in the holding body 24. A signal switching unit 26 is disposed in the holding body 24 of the upper and lower inspection units 21 and 22. The board inspection apparatus 10 includes a control unit 27 that can control the signal switching unit 26. The control unit 27 is configured as a computer including a CPU, a ROM, a RAM, and the like. The control unit 27 holds data relating to the conductor pattern and the like formed on the circuit board 11.

  Hereinafter, a specific inspection using the substrate inspection apparatus 10 will be described. As shown in FIG. 2, in the board inspection apparatus 10, probes (terminals) 151 and 152 are brought into contact with both ends of one conductor pattern 110 constituting the circuit board 11. The current supply unit 17 causes the inspection current i having a constant magnitude to flow through the conductor pattern 110 to be inspected via the probe 151 (constant current control). As shown in FIG. 2, the inspection current i flowing from one probe 151 to the conductor pattern 110 returns from the other probe 152 to the current supply unit 17 via the current measurement unit 18. As described above, the inspection current i flows in a circuit including the probes 151 and 152, the current supply unit 17, the current measurement unit 18, and the conductor pattern 110.

  By acquiring the potential difference (voltage drop) between the probes 151 and 152 at this time by the voltage measuring unit 19, the resistance value R of the conductor pattern 110 can be calculated based on Ohm's law. Based on the resistance value R thus obtained, the quality of the conductor pattern 110 (whether or not there is a short path or disconnection, the suitability of the resistance value, etc.) is determined. By performing this inspection for each of the plurality of conductor patterns 110, the quality of the circuit board 11 is determined.

  However, in such an inspection circuit, it is inevitable that a contact resistance is generated at a portion where the probes 151 and 152 and the conductor pattern 110 are in contact with each other, and this affects the measurement accuracy of the resistance value R.

FIG. 3 shows an equivalent circuit of a circuit for inspecting the conductor pattern 110 in consideration of a voltage drop due to contact resistance. In this equivalent circuit, R is the resistance of the conductor pattern 110, R _C1 is the contact resistance between the probe 151 and the conductor pattern 110, and R _C2 is the contact resistance between the probe 152 and the conductor pattern 110. . When the magnitude of the inspection current applied to the conductor pattern 110 is i, the potential difference (voltage drop) V _O detected by the voltage measuring unit 19 using the contact resistances R _C1 and R _C2 is V _O = iR. _C1 + iR + iR _C2

That is, the voltage drop V _O detected by the voltage measuring unit 19 is larger by iR _C1 + iR _C2 than the voltage drop V (= iR) due to the conductor pattern 110 to be measured. As a result, the resistance value based on the potential difference V _O measured by the voltage measuring unit 19 becomes R + R _C1 + R _C2 , which is larger than the resistance value R of the conductor pattern 110 to be measured by R _C1 + R _C2, resulting in an error in inspection. End up.

By the way, since R _C1 and R _C2 are contact resistances, they change depending on the worn state of the tips of the probes 151 and 152 and the contact state between the probes 151 and 152 and the conductor pattern 110. In particular, the tips of the probes 151 and 152 are changed. As wear begins, it tends to fluctuate significantly. In other words, the contact resistances R _C1 and R _C2 do not take a constant value and are difficult to predict in advance.

In addition, due to the characteristics of constant current control in which a constant current is always supplied to the circuit load, the probe is equivalent to the voltage drop generated by the contact resistances R _C1 and R _C2 between the probes 151 and 152 and the conductor pattern 110 in the circuit of FIG. The voltage applied between 151 and 152 increases. If the voltage applied to the conductor pattern 110 is greater than the withstand voltage, dielectric breakdown may occur in the conductor pattern 110 and the circuit board 11 may be damaged.

  In this regard, the substrate inspection apparatus 10 according to the present embodiment has the following configuration in order to solve the problems described above. Hereinafter, a detailed description will be given with reference to FIG. FIG. 4 is a diagram showing the configuration of the four-terminal method. FIG. 5 is a diagram illustrating a control loop for removing noise by the voltage correction unit 3. FIG. 6 is a diagram illustrating a configuration of the voltage correction unit 3.

  As shown in FIG. 4, the board inspection apparatus 10 includes a current supply unit 17, a current measurement unit 18, and a voltage measurement unit 19. The current supply unit 17 is a constant current source, and flows a current having a set magnitude to the conductor pattern 110 to be inspected via two current supply terminals (current measurement terminals) 153 and 154. The current measuring unit 18 detects the current flowing through the conductor pattern 110 via the two current supply terminals 153 and 154. The voltage measurement unit 19 measures the voltage of the conductor pattern 110 via the voltage measurement terminals 155 and 156.

  As shown in FIG. 4, the board inspection apparatus 10 according to the present embodiment allows a current supply unit 17 to pass a constant current to the conductor pattern 110 of the circuit board 11 to be inspected via current supply terminals 153 and 154. A so-called four-terminal method is used in which a voltage drop between the voltage measuring terminals 155 and 156 is measured by the voltage measuring unit 19.

  In the four-terminal method, since the voltage measuring unit 19 has a large internal resistance, it can be considered that the circuit provided with the voltage measuring unit 19 is substantially open. Therefore, compared with the circuit on the side where the current supply unit 17 is provided, current does not flow much in the circuit on the side where the voltage measurement unit 19 is provided, so that the current supply terminals 153 and 154 and the conductor pattern 110 The influence from the contact resistance between can be suppressed to some extent.

  By the way, as described above, in recent years, a substrate having high-density wiring close to a semiconductor is being realized by applying a semiconductor manufacturing process to substrate manufacturing. The conductor pattern (high-density fine conductor pattern) of this type of circuit board 11 has a short distance, and thus has a considerably small electric resistance value. Therefore, when this type of circuit board 11 is inspected, the influence (noise) due to the contact resistance between the measurement terminal and the conductor pattern 110 becomes relatively large.

  For example, when the resistance of the conductor pattern of the substrate having the conventional configuration is 10Ω and the contact resistance is 1Ω, the influence of the contact resistance is relatively small at about 10%. On the other hand, in the circuit board 11 on which the high-density fine conductor pattern is formed, the resistance of the conductor pattern 110 is considered to be about 3Ω, for example, and when the contact resistance is 1Ω, the influence exceeds 30%. From the viewpoint of inspection accuracy, it is not realistic.

  The situation is the same in the four-terminal method employed by the substrate inspection apparatus 10 of the present embodiment, and the contact resistance generated between the voltage measurement terminal 156 and the conductor pattern 110 cannot be ignored. In other words, in an ideal state where no noise or the like exists, the potential of the current supply terminal 154 and the potential of the voltage measurement terminal 156 are the same. A voltage drop occurs due to the contact resistance, and a potential difference is generated between the current supply terminal 154 and the voltage measurement terminal 156.

  In addition, since the contact resistance generated between the voltage measurement terminal 156 and the conductor pattern 110 is different for each contact and difficult to predict, the contact resistance between the terminal and the conductor pattern 110 is measured in advance to reduce the voltage drop. It cannot be corrected.

  In addition, if a voltage drop is detected by control of the control part 27, the structure which correct | amends the voltage for the said voltage drop is also considered. However, since the control unit 27 is often provided at a location physically separated from the circuit board 11, the control loop is also considerably long. As a result, the control unit 27 is long from the timing when the voltage drop is detected until the voltage is actually corrected. Time is required, and the efficiency of substrate inspection is greatly reduced. Further, when the control loop becomes long, noise is generated correspondingly and the accuracy of inspection is greatly reduced.

  In this regard, the substrate inspection apparatus 10 of this embodiment includes a voltage correction unit 3 as shown in FIG. The voltage correction unit 3 is disposed between the current supply terminal 154 and the voltage measurement terminal 156 and corrects a voltage drop due to contact resistance between the voltage measurement terminal 156 and the conductor pattern 110. In the present embodiment, the voltage measurement terminal 156 corresponds to the first measurement terminal, and the current supply terminal 154 corresponds to the second measurement terminal.

  The configuration of the voltage correction unit 3 will be described in detail. As shown in FIG. 6, an instrumentation amplifier 30 and an operational amplifier 40 are installed between a current supply terminal 154 and a voltage measurement terminal 156. Yes.

  The instrumentation amplifier 30 includes a non-inverting input terminal 31, an inverting input terminal 32, and an output terminal 33, and a difference between an input from the non-inverting input terminal 31 and an input from the inverting input terminal 32. Amplify. The instrumentation amplifier 30 of the present embodiment uses one having a gain of 1 (gain Gain = 1).

  The instrumentation amplifier 30 has a high common-mode rejection ratio (CMRR), a high input impedance, and high accuracy, as is widely known. Further, by using, for example, semiconductor chips as the instrumentation amplifier 30 and the operational amplifier 40, the loop for controlling the electric signal can be physically shortened. Thereby, the control speed of the control loop of the electric signal composed of the instrumentation amplifier 30 can be greatly increased, and the voltage drop due to the contact resistance can be corrected with a response speed of 1 millisecond or less, for example. It becomes possible.

  As shown in FIG. 7, the instrumentation amplifier 30 of the present embodiment includes two differential amplifiers having the same performance. As a result, common input signals from the two input terminals (in the inspection of the substrate in this description, noise due to the contact resistance, etc.) can be removed, and a high common-mode signal rejection ratio (CMRR) can be obtained. .

  The common-mode signal rejection ratio (CMRR) represents the strength of a tendency to remove an input signal (for example, noise) common to two inputs in a differential amplifier circuit or the like. That is, the greater the CMRR of the amplifier, the stronger the amplifier tends to remove common input signals such as noise.

The instrumentation amplifier 30 having a high input impedance can detect a minute electric signal. This is because the instrumentation amplifier 30 can be driven even if the input signal is small by having a high input impedance. The formula of P = I ² R is obtained from Joule's law and Ohm's law. From this formula, the driving power P of the instrumentation amplifier 30 is constant, and the larger R is, the driving current becomes larger. I becomes smaller. Accordingly, since the instrumentation amplifier 30 has a high input impedance, the instrumentation amplifier 30 can be driven even with a small electric signal. In other words, the instrumentation amplifier 30 can detect even a minute electric signal.

  As described above, the circuit board 11 having the conductor pattern (high-density fine conductor pattern) 110 has a small allowable current and withstand voltage. Therefore, when inspecting this type of circuit board 11, the current or voltage of the signal supplied to the circuit board 11 must be reduced, so that the current or voltage detected from the conductor pattern 110 is also reduced. In this regard, in the board inspection apparatus 10 of the present embodiment, the instrumentation amplifier 30 capable of detecting a minute electric signal is provided, so that the circuit board 11 having this type of high-density fine conductor pattern is inspected. Can be done without problems.

  Further, as described above, since the allowable current of the conductor pattern 110 is small, it is also necessary to reduce the current supplied to the conductor pattern 110 for inspection. Accordingly, the influence of the contact resistance generated between the voltage measurement terminal 156 and the conductor pattern 110 becomes relatively large.

  In this regard, the instrumentation amplifier 30 of the present embodiment has two differential amplifier circuits that are symmetrical to each other, and therefore noise such as a voltage drop due to contact resistance between the voltage measurement terminal 156 and the conductor pattern 110 is reduced. Can be removed.

  Next, the operational amplifier 40 shown in FIG. 6 will be described. The operational amplifier 40 includes a non-inverting input terminal 41, an inverting input terminal 42, and an output terminal 43, and has an amplification factor (gain Gain) of −1. The non-inverting input terminal 41 of the operational amplifier 40 is electrically connected to the ground, the inverting input terminal 42 is electrically connected to the output terminal 33 of the instrumentation amplifier 30, and the output terminal 43 is the instrumentation amplifier. 30 inverting input terminals 32 are electrically connected.

  The potential difference between the current supply terminal 154 and the voltage measurement terminal 156 is eliminated by removing noise such as a voltage drop due to the contact resistance between the voltage measurement terminal 156 and the conductor pattern 110 via the voltage correction unit 3 of the present embodiment. Can be corrected to zero.

  As shown in FIG. 5, the substrate inspection apparatus 10 of the present embodiment is provided with the voltage correction unit 3 between the current supply terminal 154 and the voltage measurement terminal 156, so that the current supply terminal 154, the voltage measurement terminal 156, and the conductor are provided. By quickly removing in response to noise such as a voltage drop due to contact resistance with the pattern 110, the voltage drop of the conductor pattern 110 can be stably measured, and the efficiency of the inspection of the circuit board 11 is also good. .

  Next, a specific configuration of the instrumentation amplifier 30 will be described with reference to an internal circuit of the instrumentation amplifier 30 in FIG.

  The voltage correction unit 3 of the substrate inspection apparatus 10 of the present embodiment operates the amplifier in the linear region operation state with the circuit configuration of FIG. As shown in the graph of FIG. 8, the amplifier in the linear region operating state amplifies and outputs the differential input with a constant amplification factor. In other words, the input and output of the amplifier in the operating state are proportional.

The amplifier in the linear region operating state has a characteristic of virtual short. Virtual short is a state in which the potential difference between the two inputs of the amplifier is close to zero and is virtually short-circuited. Due to this virtual short circuit, the two input voltages V ₁ and V ₁₀ are equal in the amplifier A1 of FIG. 7, and the two input voltages V ₂ and V ₂₀ are equal in the amplifier A2. Therefore, the following relational expression is obtained.
V ₁ = V ₁₀
V ₂ = V ₂₀

Assume that a common input signal such as noise is V _IC, and an output obtained by amplifying the common input signal by an amplifier is V _OC . In the circuit shown in FIG. 7, the output voltage of the amplifier A1 is V _A , the output voltage of the amplifier A2 is V _B , and the resistors arranged in the first half of the instrumentation amplifier 30 are R _g , R ₁ , R _2. Then, the following relational expression is obtained based on the above relational expression. That is,
V ₂ −V ₁ = V ₂₀ −V ₁₀ = (V _B −V _A ) R _g / (R ₂ + R _g + R ₁ ) (1)
V _OC = V _B −V _A = (R ₂ + R _g + R ₁ ) (V ₂ −V ₁ ) / R _g (2)
R _g is a resistance value that determines the gain of the instrumentation amplifier 30.

Since V _IC is a common input signal, it has the same input to each input terminal of the instrumentation amplifier 30. That is,
V _IC = V ₁ = V ₂ (3)
From the relational expressions (2) and (3), V _OC = 0 is obtained. As described above, the circuit illustrated in FIG. 7 can remove the common input signal.

  In the circuit constituting the voltage correction unit 3 of the present embodiment, the instrumentation amplifier 30 and the operational amplifier 40 are included in the control loop, and the instrumentation amplifier 30 is set to a single amplification factor. By setting the amplification factor to −1, the influence of contact resistance can be reliably removed.

  Note that, as one method for removing a voltage drop due to contact resistance, it is conceivable to use an open loop composed of a comparator. However, if the comparator has an infinite gain, the influence from the contact resistance can be surely eliminated, but such a comparator is only ideal and difficult to realize in an actual circuit.

  On the other hand, the voltage correction unit 3 of the substrate inspection apparatus 10 according to the present embodiment forms a voltage correction circuit using the stable amplification factors of the instrumentation amplifier 30 and the operational amplifier 40. Therefore, noise such as a voltage drop due to contact resistance can be reliably removed.

  As described above, the board inspection apparatus 10 of this embodiment applies an electrical signal to the conductor pattern 110 of the circuit board 11 and inspects the electrical characteristics of the circuit board 11. This board inspection apparatus includes a voltage measurement terminal 156, a current supply terminal 154, and a voltage correction unit. The voltage measurement terminal 156 and the current supply terminal 154 are in contact with the conductor pattern 110. The voltage correction unit 3 includes an instrumentation amplifier 30 that can remove noise in a circuit including a voltage measurement terminal 156, a current supply terminal 154, and a conductor pattern 110. The voltage correction unit 3 corrects the potential difference between the voltage measurement terminal 156 and the current supply terminal 154 through a control loop including the instrumentation amplifier 30.

  That is, a potential difference occurs between the voltage measurement terminal 156 and the current supply terminal 154 that should ideally have the same potential due to a voltage drop due to the contact resistance between the voltage measurement terminal 156 and the current supply terminal 154 and the conductor pattern 110. Resulting in. In addition, by detecting a voltage drop due to the contact resistance via the voltage measurement terminal 156, the detection voltage increases, and the inspection accuracy decreases. In this regard, according to the configuration described above, the voltage drop due to the contact resistance can be corrected, so that the potential difference between the voltage measurement terminal 156 and the current supply terminal 154 can be maintained to be zero. Thereby, when the circuit board 11 is inspected, the accuracy of the inspection can be further improved without being affected by the contact resistance between the voltage measurement terminal 156 and the current supply terminal 154 and the conductor pattern 110. In particular, by using the instrumentation amplifier 30 having a high common-mode signal rejection ratio (CRMM), the voltage drop due to the contact resistance between the voltage measurement terminal 156 and the current supply terminal 154 and the conductor pattern 110 is reliably corrected. can do.

  In the substrate inspection apparatus 10 of this embodiment, the instrumentation amplifier 30 includes two differential amplifier circuits that are symmetrical to each other, as shown in FIG.

  Thereby, common input signals such as noise caused by contact resistance generated between the voltage measurement terminal 156 and the current supply terminal 154 and the conductor pattern 110 can be removed, and the inspection accuracy of the circuit board 11 can be further improved.

  Further, in the substrate inspection apparatus 10 of the present embodiment, the number of amplifiers included in the control loop is two, including the instrumentation amplifier 30, the instrumentation amplifier 30 and the operational amplifier 40. Yes.

  That is, in general, the shorter the control loop for correcting the voltage drop, the faster the voltage can be stabilized. In this respect, in the present embodiment, the control loop is composed of the instrumentation amplifier 30 and one operational amplifier 40. Therefore, the control loop can be physically shortened and the moment when the voltage drop occurs. Can be corrected. Thereby, the voltage correction unit 3 can correct the voltage drop quickly and reliably.

  Moreover, in the board | substrate inspection apparatus 10 of this embodiment, the amplification factor of the instrumentation amplifier 30 is set to 1 time.

  As a result, the instrumentation amplifier 30 can stably operate at a gain of 1 ×, so that the influence of contact resistance and the like generated between the voltage measurement terminal 156 and the current supply terminal 154 and the conductor pattern 110 can be reduced. It can be removed reliably.

  The substrate inspection apparatus 10 of the present embodiment further includes an operational amplifier 40 having an amplification factor of −1.

  As described above, by using the stable amplification state of the operational amplifier 40 having an amplification factor of −1 without using the operational amplifier in the open state, the substrate inspection apparatus 10 having the highly accurate voltage correction unit 3 is realized. Can do.

  In the substrate inspection apparatus 10 of the present embodiment, the instrumentation amplifier 30 includes a non-inverting input terminal 31, an inverting input terminal 32, and an output terminal 33. The operational amplifier 40 includes a non-inverting input terminal 41, an inverting input terminal 42, and an output terminal 43. The non-inverting input terminal 31 and the voltage measurement terminal 156 are electrically connected. The inverting input terminal 32, the output terminal 43, and the current supply terminal 154 are electrically connected. The output terminal 33 and the inverting input terminal 42 are electrically connected. The non-inverting input terminal 41 is electrically connected to the ground.

  Thereby, it is possible to correct the potential difference between the voltage measurement terminal 156 and the current supply terminal 154 to be zero with a simple configuration.

  The board inspection apparatus 10 according to the present embodiment includes two voltage measurement terminals 155 and 156 and two current supply terminals 153 and 154. A current is applied to the conductor pattern 110 via the two current supply terminals 153 and 154, and the substrate is inspected using a four-terminal method in which the voltage of the conductor pattern 110 is detected from the voltage measurement terminals 155 and 156.

  Thereby, in the board | substrate inspection apparatus 10 using a 4 terminal method, the voltage drop by the contact resistance of the voltage measurement terminals 155 and 156 and the current supply terminals 153 and 154 and the conductor pattern 110 can be corrected in real time.

  The preferred embodiment of the present invention has been described above, but the above configuration can be modified as follows, for example.

  The voltage correction unit 3 is not limited to the instrumentation amplifier 30 and the operational amplifier 40, but includes only the instrumentation amplifier 30 as shown in FIG. 9, and includes a current supply terminal 154 and a voltage measurement terminal. It is also possible to correct the potential difference with respect to 156. In this case, the circuit can be further simplified.

  Moreover, the board | substrate inspection apparatus 10 of this embodiment is not limited to a 4 terminal method, It can apply also to a 2 terminal method.

3 Voltage Correction Unit 10 Board Inspection Device 11 Circuit Board 15 Probe (Terminal)
DESCRIPTION OF SYMBOLS 17 Current supply part 18 Current measurement part 19 Voltage measurement part 30 Instrumentation amplifier 31 Non-inverting input terminal 32 Inverting input terminal 33 Output terminal 40 Operational amplifier 41 Non-inverting input terminal 42 Inverting input terminal 43 Output terminal 151 Probe 152 Probe 153 Current supply terminal 154 Current supply terminal (second measurement terminal)
155 Voltage measurement terminal 156 Voltage measurement terminal (first measurement terminal)

Claims (7)

A board inspection apparatus that applies an electrical signal to a conductor pattern of a circuit board and inspects the electrical characteristics of the circuit board,
A first measurement terminal and a second measurement terminal in contact with the conductor pattern;
A voltage correction unit;
With
The voltage correction unit includes an instrumentation amplifier capable of removing noise in a circuit composed of the first measurement terminal, the second measurement terminal, and the conductor pattern,
The substrate inspection apparatus, wherein the voltage correction unit corrects a potential difference between the first measurement terminal and the second measurement terminal through a control loop including the instrumentation amplifier. The substrate inspection apparatus according to claim 1,
The instrumentation amplifier includes two differential amplifier circuits that are symmetrical to each other. The substrate inspection apparatus according to claim 1 or 2,
The number of amplifiers included in the control loop is one or two including the instrumentation amplifier. It is a board | substrate inspection apparatus as described in any one of Claim 1 to 3,
A substrate inspection apparatus, wherein an amplification factor of the instrumentation amplifier is set to 1 time. It is a board | substrate inspection apparatus as described in any one of Claim 1 to 4,
A substrate inspection apparatus, further comprising an operational amplifier having an amplification factor of -1. It is a board | substrate inspection apparatus of Claim 5, Comprising:
The instrumentation amplifier is
A non-inverting input terminal;
An inverting input terminal;
An output terminal;
With
The operational amplifier is
A non-inverting input terminal;
An inverting input terminal,
An output terminal;
With
The non-inverting input terminal and the first measurement terminal are electrically connected;
The inverting input terminal, the output terminal, and the second measurement terminal are electrically connected;
The output terminal and the inverting input terminal are electrically connected;
The substrate inspection apparatus, wherein the non-inverting input terminal is electrically connected to a ground. It is a board | substrate inspection apparatus as described in any one of Claim 1-6,
Including two voltage measurement terminals to include the first measurement terminal;
Including two current measurement terminals to include the second measurement terminal;
Inspecting a substrate using a four-terminal method in which a current is applied to the conductor pattern via the two current measurement terminals and the voltage of the conductor pattern is detected from the two voltage measurement terminals. apparatus.

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